(1) Field of the Invention
The present invention relates to a driving section of a floppy disk drive, and more particularly to a driving section in which a linear pulse motor for driving a magnetic head and a spindle motor for rotating a medium or floppy disk are unitarily formed.
(2) Description of the Related Art
In recent years, there is an increasing demand for making a floppy disk drive compact and for increasing its storage capacity. In order to meet this demand, it is necessary to develop a compact and high precision driving section of the floppy disk drive. A driving section in which a stator of a spindle motor and a stator of a linear pulse motor are unitarily formed with the elements involved being precisely positioned and the structure being made thin and compact has previously been proposed (Japanese Patent Application No. H2-299,379). Such a driving section is shown in FIGS. 1A and 1B and described herein as a prior art structure.
In order to assist the understanding of the present invention, the prior art structure referred to above is first explained with reference to FIGS. 1A, 1B and also FIG. 2. As shown in FIG. 1A, a motor base 29 carries a spindle motor stator 2 and a linear pulse motor stator 6. In the center of the spindle motor stator 2 is provided with a spindle motor bearing housing 1 which passes through the motor base 29. The linear motor stator 6 carries thereon stator-side magnetic pole pieces 5. The spindle motor is arranged such that one end of a shaft 43 of a hub 41 is inserted into the bearing housing 1 together with bearings 42 and the other end of the shaft 43 is fixed by a male screw 44 at the center of the rotor 40 from the back of the motor base 29. The rotor 40 has magnetic poles which magnetically react with the spindle motor stator 2 thereby causing the rotor 40 to rotate. The rotor 40 is supported by the bearings 42 allowing it to be rotated together with the hub 41. The rotation of the hub 41 is transmitted to the medium (not shown) whereby the medium is rotated.
The linear motor stator 6 is arranged in a projected block form at a recessed portion of the motor base 29. A primary rail 30 and a retainer 10 are provided over the linear motor stator 6. The primary rail 30 is provided with a guide groove 9 at its side portion and an opening 32 at its center portion, which opening is larger than the block form stator 6. The primary rail 30 is fixed to the motor base 29. The retainer 10 has a large opening therein with four side portions being retained. The retainer 10 has rollers at one side portion and steel balls 11 at the other portion which fit in and roll along the guide groove 9 of the primary rail 30. A reciprocating moving member 13 is provided at a location corresponding to that of the stator 6. The reciprocating moving member 13 has, as in FIG. 1B which shows a back side thereof, magnetic pole pieces 26 and a guide groove 14 at its side portion. The reciprocating moving member 13 is held by the retainer 10 in such a way that the steel balls 11 on the retainer 10 fit in and roll along the guide groove 14 of the reciprocating moving member 13. The magnetic pole pieces 26 of the reciprocating moving member 13 and the magnetic pole pieces 5 of the stator 6 are kept in position with a predetermined space provided therebetween and, due to the electromagnetic action, the reciprocating moving member 13 moves backwards and forwards in the direction defined by the guide groove 9 of the primary rail 30 and the guide groove 14 of the reciprocating moving member 13. This reciprocating moving member 13 carries thereon a magnetic head 21 as shown in FIG. 2.
Since the linear pulse motor is driven due to the electromagnetic action developed between the magnetic pole pieces 26 of the reciprocating moving member 13 and the magnetic pole pieces 5 of the stator 6 as explained above, there must be sufficient precision in the parallel relationship between the pole pieces 5 and the pole pieces 26 as, otherwise, there will develop variations in the driving characteristics. Thus, such precision in the parallel relationship must be achieved during the assemblage of the primary rail 30 to the motor base 29. What has been done in the prior art for this purpose is to provide a primary rail adjusting pivot pin 27 on the motor base 29 and to provide a pivot hole 31 for receiving therein the primary rail adjusting pivot pin 27. As the primary rail 30 has at its center portion the rectangular opening 32 which is larger than the block form stator 6, the primary rail 30 is allowed to make a slight rotation with the pivot pin 27 as the axis of rotation. By this rotation, the parallel relationship between the pole pieces 5 and the pole pieces 26 is adjusted and this is followed by the fixing of the primary rail 30 to the motor base 29.
In the manner explained above, the linear pulse motor and the spindle motor are mounted on and fixed to the motor base 29 and this results in the formation of a motor module 32 as shown in FIG. 2.
Now, how the magnetic head 21 is mounted on the motor module 32 is explained with reference to FIG. 2. For this mounting operation, a magnetic head mounting jig 34 is used. This jig 34 carries a magnetic head mounting guide pin 33 and a spindle motor shaft stopper 23. In mounting the magnetic head 21 on the reciprocating moving member 13, the center of the magnetic head 21 must be located on a straight line crossing the center of the guide pin 33 and the center of the stopper 23 (that is, the location of the diametrical direction of the medium along which the magnetic head is to scan the medium). For this purpose, there is provided a magnetic head mounting reference hole 28 in the motor base 29 at a location transversely in the center and longitudinally opposite from the location of the spindle motor. This reference hole 28 receives the guide pin 33, and the sliding movement of the guide pin 33 in the direction shown in an arrow in FIG. 2 allows the spindle motor shaft 20 to be held by the stopper 23 for mounting the magnetic head 21.
With the use of the prior art motor module 32, the moving direction of the linear pulse motor does not necessary coincide with the diametrical direction of the medium. This problem results from alignment errors in various parts such as the stator 6, the primary rail 30, the retainer 10 and the reciprocating moving member 13 constituting the linear pulse motor. That is, according to the conventional assemblage explained above, although the attention has been paid to the alignment between the magnetic pole pieces 5 of the stator 6 and the magnetic pole pieces 26 of the reciprocating moving member 13 and also to the alignment between the magnetic head 21 and the spindle motor shaft 20, no consideration has been paid to the adjustment of the magnetic head 21 with respect to the moving direction of the linear pulse motor. In the conventional motor module 32, such adjustment is structurally not possible. Thus, such conventional arrangement has encountered a problem of the magnetic head deviating from the diametrical direction of the medium during the driving operation of the linear pulse motor.